Association of type 2 Diabetes Mellitus and bone mineral density: a two-sample Mendelian randomization study

Observational studies have suggested that type 2 Diabetes Mellitus (DM2) is a potentially modifiable risk factor for lower BMD, but the causal relationship is unclear. This study aimed to examine whether the association of DM2 with lower BMD levels was causal by using Mendelian randomization (MR) analyses.

We collected genome-wide association study data for DM2 and BMD of total body and different skeletal sites from the IEU database. Subsequently, we performed a two-sample Mendelian randomization analysis using the Two Sample MR package.

We identified a positive association between DM2 risk (61,714 DM2 cases and 596,424 controls) and total BMD, and other skeletal sites BMD, such as femoral neck BMD, ultra-distal forearm BMD and heel BMD. However, non-significant trends were observed for the effects of DM2 on lumbar-spine BMD.

In two-sample MR analyses, there was positive causal relationship between DM2 and BMD in both overall samples. In summary, while observational analyses consistently indicate a strong association between DM2 and low BMD, our MR analysis introduces a nuanced perspective. Contrary to the robust association observed in observational studies, our MR analysis suggests a significant link between DM2 and elevated BMD.